First, we will generate some data frame for the purpose of demonstration.
- 2 different categories (e.g. pasta, rice)
- 4 different items (e.g. 2 of each category)
- 10 price values changes collected over time for each item
# create 4 vectors: 2x character class and 2x numeric class
item_categ <- rep(c("pasta", "rice"),each = 20)
item_ID <- rep(seq(from = 1, to = 4), each = 10)
item_ID <- paste0("ID_", item_ID)
observation_time <- rep(seq(from = 1, to = 10), times = 4)
item_price_change <- c(sample(0.5:2.5, size = 10, replace = TRUE),
sample(0:1, size = 10, replace = TRUE),
sample(2:5, size = 10, replace = TRUE),
sample(6:9, size = 10, replace = TRUE))
# use 4 vectors to create data frame with 4 columns
food <- tibble(item_ID, item_categ, observation_time, item_price_change)